Cleanup load_program() in bank.rs

[pgarg66]

Problem

The load_program function can use some streamlining and cleanup. The old code was written because of executor cache usage of bpf_loader. Since then the executor cache code has been deleted.

Summary of Changes

• Rework load_program() to remove the call to load_program_from_account()
• Remove load_program_from_account()

Fixes #

[codecov]

Codecov Report

Merging #32146 (b4bc25a) into master (faa002c) will increase coverage by 0.0%.
The diff coverage is 91.0%.

@@           Coverage Diff           @@
##           master   #32146   +/-   ##
=======================================
  Coverage    82.0%    82.0%           
=======================================
  Files         780      780           
  Lines      210860   210843   -17     
=======================================
+ Hits       172944   172963   +19     
+ Misses      37916    37880   -36     

[Lichtso]

Looks like we are missing a lot of test coverage for all the ways load_program() can go wrong.

[Lichtso]

I think this originally returned InstructionError::IncorrectProgramId in load_program_from_account() and all errors from there were turned into LoadedProgramType::FailedVerification in load_program(). But it should be unreachable, so try placing a debug_assert(solana_bpf_loader_program::check_loader_id(); here instead.

[Lichtso]

The exact error codes between load_program_from_account() and load_program() might have changed but that is irrelevant since load_program() corrects all of them again and load_program_from_account() is not used anywhere else.